<html>
  <head>
    <script type="application/ld+json">
    {
      "@context":       "http://schema.org",
      "@type":          "EmailMessage",
      "description":    "Check this out",
      "potentialAction": {
        "@type": "ViewAction",
        "target":   "https://www.youtube.com/watch?v=eH8KwfdkSqU"
      }
    }
    </script>
  </head>
  <body>
    <p>
      This a test for a Go-To action in Gmail.
    </p>
  </body>
</html>